Thermoelectric devices are especially attractive devices because they do not contain moving parts, they can be environmentally benign, and they may be easily incorporated into technologies for heat removal or for energy conversion. Thermoelectric devices, however, currently have limited use in the marketplace, which is largely a result of their low efficiencies.
While the true momentum behind research in low-dimensional thermoelectrics began in the 1990s, a limited understanding of the complex phenomena underlying the thermoelectric properties associated with low-dimensional structures has slowed progress in this area.
There has been a great deal of recent research focused on determining the optimal material systems for thermoelectric applications. The ideal electronic structure appears to include a discrete distributed density of electron states, which may be approximated by a nanostructured material that is constructed of discrete semiconductor nanocrystals. Creating this ideal material has proven very difficult because the nanocrystals are typically connected using organic surface molecules to “glue” them into a monolithic, nano-structure. These organic interconnects between the discrete nanocrystals greatly reduce the electrical conductivity and leads to poor overall material performance.
Some previous attempts have utilized zintl ions. The primary advantage of using zintl ions as nanocrystal surface ligands is to convert them into crystalline metal chalcogenides, thus linking the individual nanoscale building blocks into a macroscopic assembly of electronically coupled functional modules. This method preserves the benefits of nanostructuring and quantum confinement effects while enabling charge transport through interparticle boundaries.